Final answer:
Poisson's ratio is a measure of the ratio of lateral strain to longitudinal strain in a material. It is always less than 0.5 for an isotropic material.
Step-by-step explanation:
Poisson's ratio is a measure of the ratio of lateral strain to longitudinal strain in a material. It is denoted by the symbol ν (nu). Poisson's ratio is always less than 0.5 for an isotropic material.
This is because when a material is stretched in one direction, it tends to contract in the perpendicular direction. As a result, the material becomes thinner in the perpendicular direction and longer in the stretched direction. This phenomenon is observed in many materials, including rubber and certain metals.
For example, consider a rubber band being stretched. As it is stretched, the band becomes thinner in the perpendicular direction and longer in the stretched direction, causing Poisson's ratio to be less than 0.5.